Effect of Using Low Range Calory Coal on Electricity Production Cost and Power Plant Life

Electricity power demand has continuously decreased since the beginning of COVID-19 pandemic. In Indonesia, some coal-fired power plants have been put in reserve shutdown. Plant's competitiveness can be improved with lowering the production cost. This can be done with reducing the purchasing expenses by using cheaper lower rank coal (LRC) at different heating values. In this study, investigation is conducted to identify the operation and maintenance effects when using LRC, especially related to the plant safety and reliability, on the existing coal power plants. It is found that burning very low coal heating value, some components facilities need to increase their load until greater than its rated capacity in order to keep the maximum rated output capacity from the plants. Other effects of increased coal load are reduced boiler combustion efficiency, decreased mill temperature and increased secondary superheater temperature. These effects will lead to potential boiler failure due to the risks of increased local hotspot and erosion of the tubes. In this study, the validation method during combustion is presented to avoid these problems. This paper reported a successful study of burning a lower coal heating value of 4600 kCal/kg (ar), on 'Plant S' with 3400 MW installed capacity. More than IDR 1.5 B have been saved by replacing the original coal of typical 5000 kcal/kg (ar) with LRC, equivalent to around 1.8 TWh power generation, during June 2020. The success of this coal switching operation can be applied in other coal-fired power plants in Java-Bali grid, to obtain a better electricity production cost. Further longer period investigation is being carried out to minimize negative impact and avoiding failure during continuous operation of LRC.